A Measurement of the $W$ boson mass in 1.8 TeV $\bar{p}p$ collisions

We have determined {ital m}{sub {ital W}}=79.91{plus minus}0.39 GeV/{ital c}{sup 2} from an analysis of {ital W}{r arrow}{ital e}{nu} and {ital W}{r arrow}{mu}{nu} data from the Collider Detector at Fermilab in {ital {bar p}p} collisions at {radical}{ital s} =1.8 TeV. From this result and the world-average {ital Z} mass, the weak mixing angle is determined to be sin{sup 2}{theta}{sub {ital W}}=0.232{plus minus}0.008. An upper bound on the top-quark mass derived from this result is discussed.